Check if we should preserve more of the Context in the OpenTracing shim.

[Oberon00]

Currently when a span is created in SpanBuilderShim.start, we only have the parent OpenTracing spanContext available. This means that we lose the originial full context when calling SpanProcessor.OnStart (not yet implemented with that parameter, but see open-telemetry/opentelemetry-specification#875 and #1611 (comment).

[Oberon00]

CC @carlosalberto

[jkwatson]

@carlosalberto @Oberon00 any idea if we need this still?

[jack-berg]

Closing as I believe this is not needed. The opentracing shim spec is stable and says that spancontext and baggage are included in the context.

@carlosalberto feel free to re-open if you feel I've misinterpreted something.